I started wondering about the time frame of the Federal troop movement and it struck me that quite a bit of people and material were moved into Alexandria, Va. that May day.
The Virginia Seccession Ordinance was voted on by the people
on the 23rd of May, 1861, but passed through legislature on the 17th of April of that year. They ceded Norfolk but were adament about controlling the Potomac. One month and a few days planning. I've included the text of one of the documents all the fuss was about.

Virginia]
AN ORDINANCE to repeal the ratification of the Constitution of the
United State of America by the State of Virginia, and to resume all
the rights and powers granted under said Constitution.

The people of Virginia in their ratification of the Constitution of the
United States of America, adopted by them in convention on the
twenty-fifth day of June, in the year of our Lord one thousand seven
hundred and eighty-eight, having declared that the powers granted under
said Constitition were derived from the people of the United States and
might be resumed whensoever the same should be perverted to their
injury and oppression, and the Federal Government having perverted said
powers not only to the injury of the people of Virginia, but to the
oppression of the Southern slave-holding States:

Now, therefore, we, the people of Virginia, do declare and ordain, That
the ordinance adopted by the people of this State in convention on the
twenty-fifth day of June, in the year of our Lord one thousand seven
hundred and eighty-eight, whereby the Constitution of the United States
of America was ratified, and all acts of the General Assembly of this
State ratifying and adopting amendments to said Constitution, are hereby
repealed and abrogated; that the union between the State of Virginia and
the other States under the Constitution aforesaid is hereby dissolved, and
that the State of Virginia is in the full possession and exercise of all
the rights of sovereignty which belong and appertain to a free and
independent State.

And they do further declare, That said Constitution of the United States
of America is no longer binding on any of the citizens of this State.

This ordinance shall take effect and be an act of this day, when ratified
by a majority of the voter of the people of this State cast at a poll to
be taken thereon on the fourth Thursday in May next, in pursuance of a
schedule hereafter to be enacted.

Adopted by the convention of Virginia April 17,1861
[ratified by a vote of 132,201 to 37,451 on 23 May 1861]